A transaction object is created whenever money is debited or credited from an account.
Pending transactions are temporary and can be filtered out via the transaction status attribute.
When a connection is refreshed pending transactions are deleted and reimported, so it is recommended, not to store pending transactions, or delete them prior to a connection refresh, as they often change in amount, date and description.
When a connection is deleted and recreated, pending transactions are deleted from existing transaction data prior to retrieval of the latest data
Read more about pending transactions here.